Ultra-Stable Sodium-Ion Battery Enabled by All-Solid-State Ferroelectric-Engineered Composite Electrolytes

Highlights The capacity fading mechanism of the conventional Na3V2(PO4)3//Na3V2(PO4)3 (NVP//NVP) cell has been investigated. All-solid-state ferroelectric-engineered composite electrolyte could improve the electrolyte–electrode interfacial stability as well as the interfacial ion conduction of the Na-ion battery using the NVP anode. Outstanding cyclic stability has been achieved in the all-solid-state Na-ion battery using the NVP anode, with a capacity fading rate as low as 0.005% per cycle. Supplementary Information The online version contains supplementary material available at 10.1007/s40820-024-01474-6.

In Fig. S2, satisfied ionic conductivity is achieved in the all-solid-state ferroelectric-engineered composite electrolyte.Although the ferroelectric itself could not conduct Na + , the ceramic/polymer interfaces provide a fast ion conduction pathway for the Na + within the ferroelectric-engineered composite electrolyte.At 30 ℃, the ionic conductivity is 8.96 × 10 −5 S/cm and 1.6 × 10 −4 S/cm for the ferroelectric-engineered and non-engineered composite electrolyte, respectively.Furthermore, the electrochemical window is broadened to 5.0 V (Vs.Na/Na + ) in the ferroelectricengineered composite electrolyte, compared with the non-engineered electrolyte.S6, the NVP anode (based on V +3/+2 ) delivers abnormally high discharge capacity when using the commercial liquid electrolyte, especially in the first 5 cycles, even higher than the theoretical value (55 mAh g -1 ).However, this high capacity could not be maintained and keeps decreasing in the following cycles.Moreover, the coulombic efficiency of the cell is always less than 100% in the measured cycles, when using the liquid electrolyte.Thus, we believe the irreversible side reactions between the NVP anode and the liquid electrolyte contribute to the additional capacity.However, the continuous side reactions between 1.4 V and 1.0 V (Na/Na + ) always consumes Na + , as the capacity keeps decreasing in the measured cycles, even though the Na metal in the half cell already provides sufficient Na + .In contrast, the good cyclability could be achieved in the cell when the all-solid-state ferroelectric-engineered composite electrolyte is used, indicating the good compatibility between the NVP anode and the all-solid-state electrolyte (Fig. S6(A), (B2)).
Fig. S6 (A) Cycling performance, (B2) and (B3) differential capacity (dQ/dV) plots of the Na//NVP cells using the commercial liquid electrolyte and all-solid-state ferroelectric-engineered composite electrolyte, respectively (operation voltage range: 1.0-2.5 V, current density: 0.1C, 1C=118 mAh g -1 .) In Fig. S7, except the reversible redox reaction of V +3/+4 at ~3.4V (Na/Na + ), very tiny irreversible oxidation could also be observed in the cathode NVP from ~3.7 V to 4.0 V Vs.Na/Na + .This irreversible oxidation could be attributed to the stable CEI formation and did not affect the electrochemical performance of the NVP cathode.Figure S10 shows the XPS analyses of the anodes that were disassembled from the liquid and solid-state symmetric cells, respectively.The appearance of Na, P and V peaks is mainly attributed to the active material of NVP within the anode.With the addition of FEC in the liquid electrolyte, NaF has been successfully formed at the anode interface.Together with NaF, some organic SEI was formed, as indicated by the Cl-O/C-O peak in Fig. S10 and the C-O-C=O peak in Fig. 3.In the solid-state cell, we could not collect the signal of Si/Zr/K/Nb at the anode interface, probably because the ceramic framework within the electrolyte has been fully removed during the battery disassembly.The appearance of C-O/Cl-O peak in Fig. S10 and the C-C/C-H peak in Fig. 3 could either come from the polymer within the composite electrolyte or the binder within the anode.To further analyze the interation between PEO and NaClO4, quantum computing is calculated by Gaussian09 with B3LYP/6-311++G(d,p) basis set.Two interaction models are simulated.One is between NaClO4 and the repeated unit of PEO and the other is between NaClO4 and the end group of PEO.The interaction of NaClO4•••H-C (repeated unit) is relatively weaker, with an interaction strength of ~24.2 kJ/mol, but still much higher than the typical Van Der Waals interaction.On the other hand, the interaction between NaClO4 and the end group (-OH) is higher, with a calculated strength of 73.7 kJ/mol, and therefore could be classified as a strong hydrogen bond.

Fig
Fig. S2 (A) Ionic conductivity and (B) electrochemical window of the non-and ferroelectricengineered NaClO4/PEO-Na3Zr2Si2PO12 composite electrolytes (measured at room temperature)

Fig. S7 3
Fig. S7 3-electrode cell configuration and the voltage profile of the NVP cathode in the cell using the commercial liquid electrolyte.The measurement is conducted at room temperature

Fig. S12
Fig. S12 Simulated interaction between the NVP anode and (A) Na3Zr2Si2PO12, (B) K0.5Na0.5NbO3,(C) PEO, and (D) simulated interaction between the NVP anode and PEO with the appearance of some water molecules

Fig. S13
Fig. S13Impedance plots of the all-solid-state NVP//NVP symmetric cells using (A) nonengineered composite electrolyte and (B) ferroelectric-engineered composite electrolyte, before/at/after the redox peak potentials